Taxonomia molecular e estruturação genética populacional das baleias-de-Bryde e baleias-fin (Cetartiodactyla: Balaenopteridae)

Abstract

The current study aimed to assess the systematics of two Balaenopteridae whales using two mitochondrial markers, the cytochrome b and the control region, and the nuclear intron of α-lactalbumin. The taxonomy of the Bryde s whale complex is still unsettled, and many authors have argued whether Balaenoptera edeni (Anderson 1879) and B. brydei (Olsen, 1913) should be considered conspecific or not. We analyzed 13 specimens from the Brazilian coast (Rio de Janeiro, Paraná, Santa Catarina and Rio Grande do Sul) and sequences of 60 individuals from other regions worldwide (South African coast, Indian and Pacific Oceans) available on Genbank. Significant differences between B. edeni and B. brydei were found and our results support the hypothesis of two different species of Bryde s whale with recent divergence. The species present in the Southwestern Atlantic was identified as B. brydei and showed genetic structure with low rates of genetic diversity. According to the AMOVA results there are five distinct populations throughout the distribution of B. brydei (ΦCT = 0,854, P = 0,010): Southwest Atlantic, South Africa (Atlantic Southeast + Southwest Indian), Northeast Indian Ocean, East Indian Ocean and Northwest Pacific. The second chapter of this work investigated the subspecific status of another Balaenopteridae, the fin whale, Balaenoptera physalus, using the same molecular markers. Currently, three subspecies of fin whales were described and have been accepted: B. p. physalus Linnaeus, 1758 in the Northern Hemisphere; B. p. quoyi Fischer, 1829 in the Southern Hemisphere; and the pygmy form B. p. patachonica Burmeister, 1865, from Patagonia. Recently, molecular data has supported a fourth unnamed subspecies for the Pacific Ocean. In order to test this new hypothesis the present study analyzed 16 new samples collected in Antarctica in addition with sequences from Genbank of the tree ocean basins: North Atlantic, North Pacific and Southern Hemisphere. Cytochrome b phylogenetic reconstructions revealed a distinct clade with the North Pacific samples likewise the control region haplotype network presented a clear separation between the three ocean basins. The population fixation indices were calculated considering the whole species distribution and its results supported the differentiation of the tree ocean basins with very high levels of population structure found (ΦCT =0,517, P = 0,001) The global panmixia was in fact rejected by the AMOVA also for the North Pacific. Insofar the North Atlantic and Southern Hemisphere are probably panmictic.